Gelcasting of transparent YAG ceramics by a new gelling system

Highly transparent yttrium aluminum garnet (YAG) ceramic was prepared through spontaneous gelcasting with an aqueous mixture of commercial Al2O3 and Y2O3 powders and a water soluble co-polymer of isobutylene and maleic anhydride (commercial name Isobam) as the dispersant and gelling agent. The rheological behaviors of the slurries were investigated as a functions of Isobam concentration and solids loading. The optimized formula of the slurry was obtained with a solids loading of 68 wt% and Isobam addition 0.3 wt% (per powder). The in-line transmittances of the resulted YAG ceramic (thickness: 7.5 mm) were about 82.3% and 79.2% at the wavelengths of 1000 nm and 400 nm respectively. Microstructure observation exhibited a nearly pore-free structure with the average grain size about 15 μm. The new gelling system may have potential use for the fabrication of large and complexly shaped high quality YAG transparent ceramics.